SYS-IOUNIT(2)SYS-IOUNIT(2)NAME
iounit - return size of atomic I/O unit for file descriptor
SYNOPSIS
include "sys.m";
sys := load Sys Sys->PATH;
iounit: fn(fd: ref FD): int;
DESCRIPTION
Reads and writes of files are transmitted using the 9P protocol (see
intro(5)) and in general, operations involving large amounts of data
must be broken into smaller pieces by the operating system. The `I/O
unit' associated with each file descriptor records the maximum size, in
bytes, that may be read or written without breaking up the transfer.
The iounit system call returns the I/O unit size for the open file fd.
Certain file descriptors, particularly those associated with devices,
may have no specific I/O unit, in which case iounit will return zero.
SOURCE
/emu/port/inferno.c
/os/port/inferno.c
SEE ALSOsys-dup(2), read(5)DIAGNOSTICS
Returns zero if any error occurs or if the I/O unit size of the fd is
unspecified or unknown.
SYS-IOUNIT(2)